Variable roles of oceanic transform faults in plume dispersion along segmented mid-ocean ridges

Le résumé fourni par la source

• Three interaction modes: on-ridge, off-ridge, and on-transform–fracture zone. • Transform faults act as barrier-, bridge-, or booster-like on plume dispersion. • Roles of transforms in plume dispersion depend on plume–ridge–transform geometry. Transform faults are integral to the mid-ocean ridge system, yet their role in modulating mantle plume dispersion along segmented ridges remains poorly understood. By compiling and analyzing the tectonic characteristics of 24 global plume–ridge–transform systems, we categorize them into three types: on-ridge, off-ridge, and on-transform–fracture zone interactions. Using 3D geodynamic models, we evaluate how transform fault length, plume–transform distance, plume–ridge distance, and spreading rate influence plume behavior. Our results reveal that transform faults can play three distinct roles in plume dispersion, depending on plume positioning relative to the ridge–transform system. Barrier-like behavior occurs when transform offset increases the separation between the plume and two ridge segments and plume material needs to cross the lithospheric discontinuity boundary along the transform fault to spread, thus strongly reducing along-ridge plume dispersion (e.g., on-ridge plumes and most off-ridge plumes beneath the outside corner of a ridge segment). Bridge-like behavior arises when plumes beneath fracture zones or near ridge–transform intersections bypass these discontinuities, enabling dispersion to both ridge segments with little reduction. Booster-like behavior emerges under certain geometries, such as inside-corner plumes or plumes beneath transform centers. In these scenarios, dispersion is enhanced by shorter plume–ridge distance, avoidance of lithospheric discontinuities, and localized strengthening of along-ridge mantle flow near the transform fault induced by strike-slip motion. These findings highlight the geometric controls on plume–ridge–transform interactions and underscore the complexity of transform fault influence in plume dynamics.

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